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A Study of Brexanolone Caprilcerbate for Adults with Major Depressive Disorder With or Without Anxious Distress

Verified siteInvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study is looking at adults who have Major Depressive Disorder, which is a mental health condition that causes persistent feelings of sadness and loss of interest in daily activities. Some people with this condition may also experience anxious distress, which means they feel worried, tense, or restless along with their depression. The treatment being tested is called SPT-300, which is given as a capsule taken by mouth. The active ingredient in this medication is brexanolone caprilcerbate. The purpose of this study is to check how safe this medication is and whether people can tolerate it well when they take it over a period of time.

This is an extension study, which means it is designed for people who have already completed another study with the same medication. Participants will take SPT-300 for six weeks, and everyone in the study will receive the active medication rather than a placebo. The study is described as open-label, which means both the participants and the doctors will know what treatment is being given. During the study, participants will have regular visits where doctors will check for any unwanted effects, measure vital signs like blood pressure and heart rate, and perform blood tests and physical examinations. The doctors will also use questionnaires to assess mood, anxiety levels, and how the condition affects daily life.

Throughout the six weeks, the medical team will carefully monitor participants for any side effects or health changes. Special attention will be given to thoughts of self-harm using a specific rating scale designed for this purpose. The study will also look at whether symptoms of depression and anxiety improve over time. Participants will need to avoid alcohol and recreational drugs during the study and must use effective birth control methods if they are able to have children. The maximum daily dose of the medication is 375 milligrams, and treatment will continue for the full six-week period.

The research process

The trial runs in 10 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Entry into the extension study

    This study is an extension that lasts 6 weeks. You can enter this extension study only if you completed the previous study called SPT-300-2024-203-OUS, which means you finished Visit 6 on Day 42 of that earlier study.

    Before starting, you will need to provide written informed consent. This means you will sign a document confirming that you understand the study and agree to participate.

    You will need to agree to follow all requirements listed in the consent form and study procedures.

  2. Step 2

    Contraception requirements during the study

    If you are a woman who can become pregnant, you must not plan to become pregnant during the study and must not be breastfeeding. You will need to use at least one highly effective method of birth control during the study and for 30 days after receiving the last dose of the study medication.

    If you are a male participant, you and your female partner should agree to use at least one effective method of birth control during the study and for at least 30 days after receiving the last dose of the study medication.

  3. Step 3

    Lifestyle restrictions during the study

    You must be willing and able to avoid using drugs of abuse, including recreational or medical products containing cannabinoids, and alcohol for the entire duration of the study.

  4. Step 4

    Treatment with SPT-300

    You will receive SPT-300, which contains the active substance brexanolone caprilcerbate. The medication is provided as a capsule that you will take by mouth.

    This is an open-label study, which means both you and your doctor will know that you are receiving SPT-300. It is also a monotherapy study, meaning SPT-300 will be the only medication used to treat your condition during this study.

    The study does not specify the exact dosage, frequency, or duration of administration in the provided information. Your doctor will inform you about these details.

  5. Step 5

    Scheduled visits and assessments

    You will need to attend scheduled visits throughout the 6-week study period. The final visit is Visit 6, which occurs on Study Day 42.

    During these visits, you will undergo various assessments and tests to monitor your safety and how you are responding to the treatment.

  6. Step 6

    Safety monitoring

    Throughout the study, the medical team will monitor you for any adverse events, which are unwanted or harmful effects that may occur during treatment. This includes tracking the frequency, severity, and duration of these events.

    You will have regular checks of your vital signs, such as blood pressure and heart rate.

    You will undergo electrocardiograms, which are tests that measure the electrical activity of your heart.

    You will have laboratory tests performed on samples of your blood or other body fluids to check for any changes in your health.

    You will have physical examinations to assess your overall health.

  7. Step 7

    Suicide risk assessment

    Your doctor will regularly assess you for suicidal thoughts and behaviors using a tool called the Columbia Suicide Severity Rating Scale. This is a questionnaire that helps identify if you are having thoughts of harming yourself.

  8. Step 8

    Depression and anxiety assessments

    Your symptoms of depression will be measured using the HAM-D-17, which is a 17-item questionnaire that assesses the severity of depression.

    Your overall illness severity will be assessed using the CGI-S, which stands for Clinical Global Impression - Severity scale. This is a rating by your doctor of how severe your condition is.

    Your anxiety symptoms will be measured using the Hamilton Anxiety Rating Scale.

    You will be asked to rate your own impression of your illness severity using the PGI-S, which stands for Patient Global Impression - Severity.

    These assessments will be compared from the beginning of the study to Visit 6 on Study Day 42 to see if there are any changes.

  9. Step 9

    Quality of life and functioning assessments

    Your level of disability will be assessed using the Sheehan Disability Scale, which measures how much your symptoms interfere with your work, social life, and family life.

    Your quality of life will be measured using The Quality of Life, Enjoyment, and Satisfaction Questionnaire-Short Form. This questionnaire asks about your satisfaction with different areas of your life.

    These assessments will be compared from the beginning of the study to Visit 6 on Study Day 42 to see if there are any changes.

  10. Step 10

    Completion of the study

    The study will be completed after 6 weeks, at Visit 6 on Study Day 42.

    You will need to continue following the contraception requirements for 30 days after your last dose of study medication.

Who can join the trial?

8 criteria

  • You must have completed treatment in the previous study called SPT-300-2024-203-OUS, which means you finished Visit 6 on Day 42 of that study
  • You must be able and willing to provide written informed consent, which is a document you sign to show you understand and agree to participate in the study, before any study procedures begin
  • You must agree to follow all requirements and restrictions listed in the informed consent form and in the study plan
  • If you are a woman who can become pregnant, you must not be planning to become pregnant during the study and must not be currently breastfeeding, which means nursing a baby
  • If you are a woman who can become pregnant, you must agree to use at least one highly effective method of birth control during the study and for 30 days after taking the last dose of the study medicine
  • If you are a male participant, you and your female partner must agree to use at least one effective method of birth control during the study and for at least 30 days after taking the last dose of the study medicine
  • You must be willing and able to avoid using drugs of abuse, which are illegal or recreational drugs, including recreational cannabinoids (such as marijuana) or medical cannabinoids (cannabis products prescribed by a doctor), and alcohol for the entire duration of the study
  • You must be willing and able to attend all scheduled visits, follow the treatment plan, complete laboratory tests, and meet other study requirements

Who cannot join the trial?

3 criteria

  • The specific exclusion criteria (reasons why you cannot participate) have not been provided in the available study information
  • Generally, clinical trials have requirements about your health conditions, medications you take, and other factors that might affect your safety or the study results
  • You will need to discuss with the study doctor whether you meet all requirements to participate safely in this research
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Investigated drugs

SPT-300 is an investigational medication being studied as a treatment for major depressive disorder in adults. In this clinical trial, it is given by mouth as the only medication treatment to see how safe it is and how well people tolerate it over a 6-week period. The study is looking at its effects in people who have depression, whether or not they also experience anxious distress.

What is already known about the treatment

SPT-300 – SPT-300 is an oral medication currently being studied in clinical trials for the treatment of Major Depressive Disorder, which may occur with or without feelings of anxious distress. This medication is taken by mouth and is being evaluated as a single-drug treatment to understand how safe it is and how well people tolerate it when used for depression. The study aims to gather important information about its effects on adults suffering from this mental health condition. At this stage, SPT-300 is an investigational drug, meaning it is still being tested and has not yet received full approval for widespread medical use.

Investigated diseases

Major Depressive Disorder – Major Depressive Disorder is a mental health condition characterized by persistent feelings of sadness, hopelessness, and loss of interest in activities that were once enjoyable. People with this disorder experience these symptoms for at least two weeks, and the symptoms significantly interfere with daily functioning. The condition affects mood, thoughts, behavior, and physical health, leading to difficulties in work, relationships, and self-care. Some individuals with Major Depressive Disorder may also experience anxious distress, which includes feelings of tension, restlessness, and worry occurring alongside depressive symptoms. The disorder can vary in severity and may occur as a single episode or recur multiple times throughout a person's life. Without appropriate care, symptoms can persist for months or years, significantly impacting quality of life.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-522347-18-00Protocol codeSPT-300-2024-204Estimated enrolment379 patientsSponsorSeaport Therapeutics Inc.

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